Effects of time reversal on consonant identification

Abstract

Time-reversed speech has the same long-term amplitude spectrum as natural speech, but is largely unintelligible. To study the perceptual effects of disrupting the temporal integrity of formant transitions on consonant identification, CVC syllables were divided into brief, successive, nonoverlapping segments and each segment was time reversed. In experiment 1, CVC syllables from two talkers were time reversed using 20, 40, 60, 80, or 100-ms temporal windows. The initial consonant was either /p/, /t/, /k/, /b/, /d/, /g/, /s/, /∫/, /f/, or /v/. The medial vowel was /i/, /u/, or /ʌ/, and the final consonant was /t/. Identification accuracy (12 listeners) showed a progressive decline from 99% for unmodified syllables to 63% for the 100-ms window. Time reversal was less disruptive when syllables were presented in a natural carrier sentence, dropping to 75% for a 100-ms time window. Experiment 2 replicated this pattern of findings with a larger sample of ten talkers. The effects of time reversal were not uniform across the 12 consonants, but showed highly disruptive effects on the identification of stops and relatively minor changes in fricatives. Overall, the results suggest that time reversal provides a useful method for quantifying the role of dynamic information in consonant perception.